In addition to Sir Joshua Reynolds (knighted 1768), other artists included Sir Thomas Lawrence (1815), Sir William Beechey (1798), Sir Samuel Romilly (1806), Sir George Hayter, Sir William Allan, Sir David Wilkie, Sir Martin Archer Shee, Sir Nathaniel Dance... the list goes on. Sir Francis Leggatt Chantrey was a sculptor. Sir Joseph Paxton was a landscape gardener and architecht. Sir William Herschel (1738-1822) was an astronomer. Sir Marc Isambard Brunel (1769-1849) was a civil engineer. Lots more at the NPG where these came from. (Can't find any pre-Victorian actors, though.)

Knights Bachelor and Knights Banneret are included in the tables of precedence in my 1812, 1818, 1828, and 1865 peerages. Is there a good website explaining these terms? I can't find one.

In 1828 the Order of the Garter included (in addition to a dozen foreign sovereigns and all the royal dukes) ten dukes, seven marquesses, and six earls. The Order of the Thistle was more select, including only the sovereign, one royal duke, one non-royal duke, three marquesses, ten earls, and one viscount. The Order of the Bath is much larger, and limited to mostly military men; in 1815, three classes of the Order of the Bath were established, the details being too long and complicated to post here. The Order of St. Patrick was similar in makeup and numbers to the Order of the Thistle, only it was Irish. The Order of St. Michael and St. George was created in 1818 and restricted to non-Britons serving in the Ionian islands and Malta.

As for Sir William Lucas, I agree with Shinjinee and Caroline that his elevation probably involved money and little more of significance, except of course that he apparently went to Court at St. James's to receive the knighthood and it made a lasting impression on him. I wonder that he did not make an effort to have his offpsring presented at Court, even if he could not afford to take them to London for the Season.